Until that blockbuster tweet, the Celtics had somehow kept their courtship of Butler University’s baby-faced star coach quiet, a near-impossible feat in a social media era when secrets don’t seem to stay secret for long.

Stevens said he didn’t realize one year had passed until he received a few text messages about it on Thursday.

But looking back, he recalled a mix of emotions about the time leading up to being announced as the 17th coach in Celtics history.

“It was tough because any time you’re looking at making a major life change, you’ve got to be very thorough in assessing and analyzing everything,” he said. “Obviously, those few days were tough, but that was a good problem to have. That’s what I remember from it. It was pretty emotional leaving that day. There’s no question about it. But I was glad that the [Butler] players got to hear it from me first and nobody else.”

‘I feel great one year later. Frustrated, always disappointed, with the season we had . . . but I’m so much more ready for . . . Year 2.’

The process began weeks earlier. Right after Doc Rivers left his post as Celtics coach to join the Los Angeles Clippers, Danny Ainge’s first call was to Stevens, which caught him off guard.

“Yeah, obviously you’re flattered and it’s an honor,” Stevens said. “And then we just decided that we’d talk later that weekend.”

And so they did — and they just kept talking.

Then, on the morning of July 3, Celtics management flew via private jet from Hanscom Field in Bedford to Indianapolis Executive Airport in Zionsville, Stevens’s hometown.

Celtics owners Wyc Grousbeck and Steve Pagliuca, as well as Ainge, their president of basketball operations, and assistant general manager Mike Zarren, who is also the team’s legal counsel, were taken to Stevens’s mother’s house, where he and his wife were living while between homes.

After a long chat, Ainge left a signed contract on the table. Stevens signed it that day. Two days later, at the Celtics’ training facility here in Waltham, he was introduced as Rivers’s replacement. By then, Stevens said he hadn’t slept for days.

“It was emotional because you’ve been at a place for 13 years,” Stevens said of his time at Butler, where he got his coaching start. “That place [Indiana] was also home for 33 years. There were a lot of emotions that were going through you, but you’re excited about a new challenge, you realize that you’ve got a lot to learn, and that’s hammered home when you get into the summer league and you’ve got to hire a staff and you’ve got to work with people that you’ve never worked with before.”

He added, “I feel great one year later. Frustrated, always disappointed, with the [past] season we had, but I feel like from a knowledge standpoint and an awareness standpoint, I’m so much more ready for this summer league in Year 2.”

The Celtics will be in Orlando for summer league, and they open competition Saturday against the Miami Heat.

Yet as Stevens said, frustration lingers from his first NBA season, when the Celtics posted a 25-57 record, the third-worst mark in franchise history.

Has he moved on from it? Not yet.

“No, I don’t think I ever will,” said Stevens, who can also recall with great detail almost every loss from his six years as head coach at Butler. “Every season you learn from and grow from. I don’t move on from anything. But at the same time, it doesn’t define you, either.”

It’s hard for Stevens to believe a year has passed.

“It’s flown by. Obviously, we really, really like it here,” he said of Boston. “We’re also pleased that we’ve got such a great relationship and are so connected to Butler. It’s been a great transition for us.”